The visual and functional impacts of astigmatism and its clinical management

Abstract

Purpose: To provide a comprehensive overview of research examining the impact of astigmatism on clinical and functional measures of vision, the short and longer term adaptations to astigmatism that occur in the visual system, and the currently available clinical options for the management of patients with astigmatism. Recent findings: The presence of astigmatism can lead to substantial reductions in visual performance in a variety of clinical vision measures and functional visual tasks. Recent evidence demonstrates that astigmatic blur results in short-term adaptations in the visual system that appear to reduce the perceived impact of astigmatism on vision. In the longer term, uncorrected astigmatism in childhood can also significantly impact on visual development, resulting in amblyopia. Astigmatism is also associated with the development of spherical refractive errors. Although the clinical correction of small magnitudes of astigmatism is relatively straightforward, the precise, reliable correction of astigmatism (particularly high astigmatism) can be challenging. A wide variety of refractive corrections are now available for the patient with astigmatism, including spectacle, contact lens and surgical options. Conclusion: Astigmatism is one of the most common refractive errors managed in clinical ophthalmic practice. The significant visual and functional impacts of astigmatism emphasise the importance of its reliable clinical management. With continued improvements in ocular measurement techniques and developments in a range of different refractive correction technologies, the future promises the potential for more precise and comprehensive correction options for astigmatic patients.

Astigmatism and its components in 12-year-old Chinese children: the Anyang Childhood Eye Study

“…Astigmatism is a common eye condition in children as well as in adults 1. Total, or refractive astigmatism (RA) is a combination of a corneal component (CA) and an internal astigmatism component arising from the lens (IA).…”

Amblyopia: neural basis and therapeutic approaches

“…Astigmatism, on the other hand, is detected when the vertical diopter value differs from the horizontal value (22) . Astigmatism is the most common refractive error associated with amblyopia (12) as it substantially affects visual system development (25) . The term meridional am blyopia is commonly used to refer to amblyopia caused by astigmatism.…”

“…The strabismic eye may fail to receive visual stimuli onto the macular area (31) , thus affecting various developmental stages of cortical processing (16) . Identification of factors that cause strabismus may be important for diagnosis and treatment of amblyopia (25) .…”

Calculations of actual corneal astigmatism using total corneal refractive power before and after myopic keratorefractive surgery

“…[5] In traditional keratometry measuring only the anterior corneal surface, a fixed correlation between the anterior and posterior corneal surface is assumed and the standardized keratometric refractive index of 1.3375 is used. [3] However, the standardized keratometric refractive index is selected arbitrarily, and the net power of the cornea is less than the standardized keratometric power. [6] In addition, the relationship between the anterior and posterior corneal astigmatism is not fixed as a function of age:[3,7–9] the anterior corneal astigmatism is usually with-the-rule (WTR) astigmatism in younger age groups, but predominantly against-the-rule (ATR) astigmatism in older age groups.…”

“…[3] However, the standardized keratometric refractive index is selected arbitrarily, and the net power of the cornea is less than the standardized keratometric power. [6] In addition, the relationship between the anterior and posterior corneal astigmatism is not fixed as a function of age:[3,7–9] the anterior corneal astigmatism is usually with-the-rule (WTR) astigmatism in younger age groups, but predominantly against-the-rule (ATR) astigmatism in older age groups. In contrast, the posterior corneal astigmatism remains relatively stable in magnitude and ATR axis, regardless of age.…”